Hundreds of soldiers and mercenaries were killed in a battle for a disputed oil field, the Sudanese government claims.

Nafie Ali Nafie, a top aide to Sudan's president Omar al-Bashir, said the death toll in the battle for Heglig "amounted to 400", according to the Sudanese Media Centre which is close to the security apparatus.

Heglig is Sudan's most important oil field but was seized by troops from South Sudan on April 10.

On Sunday, South Sudan's army said it had withdrawn from the area, ending a deadly stand-off which forced thousands of civilians to flee.

However the casualty figures given by Sudan were impossible to verify.

Heglig is internationally regarded as part of Sudan, although South Sudan disputes it.

The 10-day occupation by the world's newest nation met widespread criticism, including from United Nations chief Ban Ki-moon, who called it illegal.

Foreign powers have also called for an end to Sudan's cross-border air raids.

Sudan's oil minister Ishaq Adam Gamaa said the chance of the sides reaching a settlement soon was now "very remote" and said Khartoum would probably demand compensation for damage to Heglig before returning to talks.

Sudan lost about 40,000 barrels per day of output because of the fighting, he said, but added the country had enough reserves to last up to six months before the impact would be felt in its refineries.

Tensions have mounted since South Sudan declared independence from Sudan in July last year under a peace settlement which ended decades of civil war between the two sides.